Search results for "mathématique"

Adapter localement les prévisions climatiques saisonnières : désagrégation stochastique et interpolation spatiale.

2013

6 pages; International audience; Un panorama est fait des méthodes de descente d’échelles permettant de passer de prévisions climatiques saisonnières de large-échelle à des séries locales journalières. L’exemple des générateurs stochastiques de temps est appliqué à la prévision des récoltes de sorgho au Kenya, dans le cadre du programme ANR PICREVAT. Une méthode d’interpolation spatiale des paramètres des générateurs est testée, pour obtenir des séries journalières de précipitations en tout point du territoire. Les séries générées sont utilisées en entrée du modèle agronomique SARRA-H.

Climatic gradients along the windward slopes of Mount Kenya and their implication for crop risks. Part 2 : crop sensitivity.

2016

16 pages; International audience; Mount Kenya is an equatorial mountain whose climatic setting is fairly simple (two rainy seasons in March–May, the Long Rains, and October–December, the Short Rains) though concealing significant spatial variations related to elevation and aspect (part I, Camberlin et al., 2014). This part II is dedicated to the sensitivity of sorghum yields to climate variability in space and time, with a focus on the intra-seasonal characteristics of the rainy seasons. To that aim we use the crop model SARRA-H calibrated for the region and fed with rainfall, temperature, wind speed, humidity and solar radiation data over the period 1973–2001 at three stations located on t…

Solid-solid phase transition in hard ellipsoids

2009

We present a computer simulation study of the crystalline phases of hard ellipsoids of revolution. A previous study [P. Pfleiderer and T. Schilling, Phys. Rev. E 75, 020402 (2007)]. showed that for aspect ratios a/bor=3 the previously suggested stretched-fcc phase [D. Frenkel and B. Mulder, Mol. Phys. 55, 1171 (1985)] is unstable with respect to a simple monoclinic phase with two ellipsoids of different orientations per unit cell (SM2). In order to study the stability of these crystalline phases at different aspect ratios and as a function of density we have calculated their free energies by thermodynamic integration. The integration path was sampled by an expanded ensemble method in which …

Six lettres de Giuseppe Peano à Robert de Montessus de Ballore

2012

Nous transcrivons et analysons six lettres inédites que Giuseppe Peano a adressées au mathématicien français Robert de Montessus de Ballore entre 1896 et 1902. Nous montrons comment ces lettres témoignent de l'activité mathématique des deux scientifiques.

Gravity-induced liquid crystal phase transitions of colloidal platelets.

2004

he influence of gravity on a suspension of sterically stabilized colloidal gibbsite platelets is studied. An initially isotropic-nematic biphasic sample of such a suspension develops a columnar phase on the bottom on prolonged standing. This phenomenon is described using a simple osmotic compression model. We performed Monte Carlo simulations of cut spheres with aspect ratio L/D = 1/15 and took data from the literature to supply the equations of state required for the model. We find that the model describes the observed three-phase equilibrium quite well.

Tuning the defect configurations in nematic and smectic liquid crystalline shells

2013

Thin liquid crystalline shells surrounding and surrounded by aqueous phases can be conveniently produced using a nested capillary microfluidic system, as was first demonstrated by Fernandez-Nieves et al. in 2007. By choosing particular combinations of stabilizers in the internal and external phases, different types of alignment, uniform or hybrid, can be ensured within the shell. Here, we investigate shells in the nematic and smectic phases under varying boundary conditions, focusing in particular on textural transformations during phase transitions, on the interaction between topological defects in the director field and inclusions in the liquid crystal (LC), and on the possibility to rel…

Late Frasnian Atrypida (Brachiopoda) from the Ardenne shelf (southern Belgium)

2004

Enhancing $l_i 3 l_j$ with the $Z^0$-penguin

2012

OMC: An Optical Monitoring Camera for INTEGRAL - Instrument description and performance

2003

The Optical Monitoring Camera (OMC) will observe the optical emission from the prime targets of the gammaray instruments onboard the ESA mission INTEGRAL, with the support of the JEM-X monitor in the X-ray domain. This capability will provide invaluable diagnostic information on the nature and the physics of the sources over a broad wavelength range. Its main scientific objectives are: ( 1) to monitor the optical emission from the sources observed by the gamma- and X-ray instruments, measuring the time and intensity structure of the optical emission for comparison with variability at high energies, and ( 2) to provide the brightness and position of the optical counterpart of any gamma- or X…

Studies on the response of a water-Cherenkov detector of the Pierre Auger Observatory to atmospheric muons using an RPC hodoscope

2020

Extensive air showers, originating from ultra-high energy cosmic rays, have been successfully measured through the use of arrays of water-Cherenkov detectors (WCDs). Sophisticated analyses exploiting WCD data have made it possible to demonstrate that shower simulations, based on different hadronic-interaction models, cannot reproduce the observed number of muons at the ground. The accurate knowledge of the WCD response to muons is paramount in establishing the exact level of this discrepancy. In this work, we report on a study of the response of a WCD of the Pierre Auger Observatory to atmospheric muons performed with a hodoscope made of resistive plate chambers (RPCs), enabling us to selec…